1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine or a facsimile apparatus, capable of reading an image and executing a predetermined process thereon.
2. Related Background Art
Conventionally there is already known an image forming apparatus capable of image reading with a color scanner and outputting the read image as a color image or a monochromatic image. Such color scanner effects image reading by illuminating the original image with a white light source and reading the illuminated original image with red, green and blue sensors, or by switching the color of the light source.
However, in the above-mentioned conventional image forming apparatus, the image reading with the red (R), green (G) and blue (B) sensors has been associated with a drawback of requiring complex signal processing for effecting positional compensation of the image reading sensors, in order to exactly reproduce the read color image.
On the other hand, the system of switching the color of the light source does not require such positional compensation, but inevitably leads to a larger dimension of the apparatus because three fluorescent lamps of red, green and blue colors are required. Also the fluorescent lamps, requiring a certain time for the stabilization of the light emission, are inadequate for use in the image reading device of so-called sheet-through type, in which the image is read while the original is transported. Consequently such light source-switching system can only be used in the image reading device of so-called book-reading type in which the image is read while the original is fixed. Also in case the characteristics are different among different colors, it has been difficult to achieve fine adjustments for example of the lamp lighting time, since the fluorescent lamps require a certain time for stabilization as mentioned above.